The serious political polarization of the United States in 2020 is rarely seen since the U.S. civil war. The last stage of Trump’s term of office has brought a huge impact on American politics and society，and also made the 2020 general election extremely divided. In order to win the election，the Democratic party and Republican party blame each other that the other side will bring disastrous consequences to the country. As a result of the election，Joe Biden won 306 electoral votes to become the 46th president of the United States. Trump won 232 electoral votes. The Democrats came back to power four years later. Trump is the fourth president in the past 100 years who failed in reelection. Despite the announcement of the election result，the economic downturn and social contradictions which are aggravated by COVID-19，as well as the long-standing social inequality between the rich and the poor，still remain a great confusion and worry for many Americans. The resolution of the domestic crisis in the United States will be a long-term and unstable process，which will also add variables to international politics and economy.